feat: sync bot keyboards and callbacks

Sync telesrv b96f2dd (feat(bot): complete keyboards callbacks and durable delivery).

Skipped private docs and preserved public README files per sync rules; normalized the appearance seed log label for public naming.

internal/store/postgres/message_markup_codec_test.go

@@ -0,0 +1,42 @@
+package postgres
+
+import (
+	"testing"
+
+	"telesrv/internal/domain"
+)
+
+func TestReplyMarkupCodecValidatesTaggedUnion(t *testing.T) {
+	keyboard := &domain.MessageReplyMarkup{
+		Type:        domain.MessageReplyMarkupKeyboard,
+		Keyboard:    [][]domain.MarkupButton{{{Type: domain.MarkupButtonText, Text: "Help"}}},
+		Resize:      true,
+		Placeholder: "Choose",
+	}
+	raw, err := encodeReplyMarkup(keyboard)
+	if err != nil {
+		t.Fatalf("encode reply keyboard: %v", err)
+	}
+	got, err := decodeReplyMarkup(string(raw))
+	if err != nil || got == nil || got.Kind() != domain.MessageReplyMarkupKeyboard ||
+		len(got.Keyboard) != 1 || got.Keyboard[0][0].Text != "Help" || !got.Resize || got.Placeholder != "Choose" {
+		t.Fatalf("decoded reply keyboard = %#v, err=%v", got, err)
+	}
+
+	// Pre-union inline snapshots intentionally remain readable.
+	legacy, err := decodeReplyMarkup(`{"inline":[[{"type":"callback","text":"OK","data":"b2s="}]]}`)
+	if err != nil || legacy == nil || legacy.Kind() != domain.MessageReplyMarkupInline {
+		t.Fatalf("legacy inline markup = %#v, err=%v", legacy, err)
+	}
+
+	malformed := &domain.MessageReplyMarkup{
+		Type:     domain.MessageReplyMarkupInline,
+		Keyboard: [][]domain.MarkupButton{{{Type: domain.MarkupButtonText, Text: "wrong"}}},
+	}
+	if _, err := encodeReplyMarkup(malformed); err == nil {
+		t.Fatal("malformed union must fail at the write boundary")
+	}
+	if _, err := decodeReplyMarkup(`{"type":"inline","keyboard":[[{"type":"text","text":"wrong"}]]}`); err == nil {
+		t.Fatal("malformed stored union must fail at the read boundary")
+	}
+}